<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<script>
    // 变量声明
    let age = 10
    // 变量修改
    age = 20

    let name = '南风' // let age = 100 变量不能重复声明

    // 控制台输出
    console.log('年龄是:' + age)
    console.log('姓名是:' + name)

    // 在body中输出
    let username = prompt('请输入用户名:')
    document.write(username)
</script>
</body>
</html>
